Method of filtering or dewatering



Dec. 19., 1939. e Rupp rAL 2,183,896

METHOD QF FILTERING QR DEWATERING Filed June 1, 193? 2 sheets-sh et 1 v INVENTOR GEO/P66 RUFF by .v PH/L/P M. F/?A/V 7z v 1939- G. H. RUPP ET AL 2,1 3,896

METHOD OF FILTERING 0R DEWATERING Filed June 1, 1957 2 Sheets-Sheet 2 ATTORNEY Patented Dec.19,1939

METHOD OF FILTERING OR- DEWATERING A PATENT OFFICE George H. Rupp" and Philip M. Frantz, Pueblo,

(1010., assignors to Th Corporation, Denver,

Application June 1, 1

e Colorado Fuel and Iron Colo.

937, Serial No. 145,832

6 Claims. (01. 210-149) This invention relates to filtering and more particularly relates to a dewatering operation in the treatment of a mass of solids in wet condition or in liquid suspension.

It is a primary object of the present invention to utilize solids of various sizes in the material under treatment as a filtering medium, to prevent the passage through the solids body of particles an infinite variety of particles of size finer than the passages in a porous filtering I medium on which the material is supported.

Another object of the invention is the maintenance of a body of solids, while filtering, in an essentially unstratified condition throughout the operation, to adapt such body to function as a filtering medium in the filtering operation.

A further object of the invention is the production and maintenance of a pool in which the solids in the material under treatment are initially settled and from which they move by the impetus of difierential vibrations along an inclination to an elevated point of discharge above the pool.

Still another object of the invention is the v 25 direction of vibratory impulses against a body of material under treatment on an inclined surface at a predetermined angle thereto.

A still further object of the invention is to provide a method of dewatering pulps such as 30 coal concentrates andv like materials in compacted condition by controlling the direction of travel of the solids in compacted condition through a dewateringzone.

Other objects reside in novel steps and treat- 'ments, all of which will appear more fully in the course of the following description.

It has long been known that the froth flotation process of mineral concentration may be used as a medium to effectively separate coal from ash and other worthless or unmarketable constituents with which it is associated in its natural formation.

Many methods have been devised for a concentration of this character and highly satisfactory results may be attained in producing a coal concentrate of essentially clean condition. For example, the coal flotation process described and claimed in United States Letters Patent No. 2,- 028,742 of Philip M. Frantz hasbeen found to produce a highly satisfactory coal concentrate.

Concentration of coal by the froth flotation process has never attained widespread commercial acceptance by reason of the fact that the coal concentrate after separation cannot be effectively dewatered by any of the well-known methods of dewatering usually used in connection with dewatering of the froth concentrates of the various flotation processes.

The present invention had its inception in the desire to provide a method of dewatering 5 of coal concentrates of flotation in. an economical manner, which would render such treatment feasible commercially.

Unlike the concentrates of most flotation processes which are of relatively high market value, theconcentrate of the coal flotation treatment which has a large volume per unit of weight, is a product relatively cheap by comparison and consequently requires cheap treatment methods. The well-known dewatering treatments, such as rotary filters, shaking screens'and the like, are not effective for the treatment of the coal concentrate of flotation, and for this reason that process has never come into widespread commercial usage.

Applicants, after investigating many types of different apparatus for dewatering solids and liquids, discovered that if any dewatering treatment for coal concentrates on a profitable basis was to be utilized, it would require the developmerit of new apparatus and methods. The present invention represents the culmination of their efforts in this connection and has been found to provide a, cheap and effective method for dewatering of coal concentrates or other masses of wet solids possessing similar characteristics and presenting corresponding problems.

Various apparatus may be devised for performing the steps and treatments of the present invention and in our co-pending application Serial No. 10,670, Patent'No. 2,089,548 of- August 10, 1937, we have described and claimed the filter construction effective for performing the process of the present invention. 'Features disclosed but not claimed in the present application 40 have been made the subject matter of claims in the aforesaid co-pending application, of which the present application is a continuation-in-part.

Briefly stated, the present invention involves a filtering treatment in .which a pulp, such as coal, in a water suspension varying from twenty to fifty per cent solids, for example, is initially introduced into a pool formed on the bottom of a vibrating filter, said bottom comprising a filter medium and extending at an inclination to an elevated point of discharge above the upper surface of the pool.

During the operation, the filter is subjected to the actionof vibrators producing rapid diiferential vibrations. Water is moved rapidly through the filtering medium, causing a downward current of high velocity that induces almost instantaneous formation of a layer of solids at the bot-- tom of the pool, and the layer progressively increases in thickness so long as there is a pool of water and solids above the formed layer or cake.

While the cake is being" formed, it is also being compacted by the vibrations due to the inertia of the pool, trapping the finer particles of solids and thereby preventing them from being carried through the meshes of the filter cloth. In the formation of the cake, there is no grading action and an examination of the finished cake will disclose very little segregation of the various sizes of the solids, many of the larger sizes being at the top of the cake as indicated in Figure 3.

Unlike other filtering actions, the cake does not become impervious to the passage of water since there is no segregation and hydraulic grading of sizes. There is a compacting of mixed sizes under the impact of the differential vibrations of high frequency and small amplitude,butthere is also a slight movement of the individual particles that tends to keep the cake permeable to water no matter how tightly it packs as it ascends the inclined bottom.

In this way, the cake is adapted to act as a filtering medium, and in fact, is the main filtering medium for all sizes smaller than the mesh of the filter cloth.

In our Patent No. 2,089,548, we have emphasized the importance of uniformity of vibratory impulses at all points on the filter surface and in establishing such uniformity, we have pointed out the advisability of constructing the filter frame of component parts all of the same degree of elasticity. We have also pointed out the advantage derived from having the reenforcing members 8 inclined in substantial alinement with the shaft 20, which in turn preferably is at an angle of approximately forty-five degrees to the filter surface. This construction constitutes the direction control for the progressive movement ofthe cake through the pool and to the elevated point of discharge, the distance traveled from the pool to the point of discharge being sufficient to thoroughly dewater the solids under the influence of the differential vibrations.

Thus we see that because of its inertia the pool functions as a control element to properly form the cake initially, as well as controlling its movement in the initial stages toward the point of discharge, and the controlled vibratory movement imparts to the cake a progressive movement which is rendered substantially uniform at all stages by the filter construction, to prevent any deviation from its prescribed course parallel with the inclined bottom and to insure proper dewatering by the time the cake passes across the discharge.

During the entire period from its formation until it discharges, the cake remains in a permeable condition and functions as an effective filtering medium, particularly for the finer sizes, which would otherwise pass through the screen'with the filtrate.

Having thus described the principal feature of the process constituting the present invention,

reference will now be made to the accompanying drawings in which apparatus effective for performing the process has been illustrated. It will be understood that the apparatus shown is merely typical of what may be used in performing the process and obviously other structural forms may be produced for performing the various steps and treatments described herein.

In the drawings, in the several views of which like parts have been similarly designated,

Figure 1 is a plan view partially in section, of a vibrating filter effective for performing the process of the present invention;

Figure 2 is a longitudinal section taken on the line 22 of Figure 1;

Figure 3 is a transverse section on the line 33 of Figure 2, and drawn to a larger scale;

Figure 4 is a diagrammatic illustration of apparatus designed to perform the process of the present invention; and

Figure 5 is a side elevation of a vibrating filter similar to the one illustrated in Figures 1, 2 and 3, and illustrating a preferred form of spring suspension therefor.

In the drawings numeral I denotes a rectangular frame, preferably made of light structural steel, such as angle irons. Transverse reenforcing members are shown at 8, these being wider at their center points than at their extremities to provide a beam of substantially uniform rigidity. Triangular-shaped sides 9 and I are each flanged at I2 along their respective lower edges, whereby they are securely fastened to the longitudinal sides of the frame 1 by means of a plurality of bolts or rivets I3. The triangular shape of the sides is for the purpose of supplying rigid means to transmit vibrations to the frame as .will be more fully disclosed below.

Clamped between the frame I and the flanges I2 is a perforated screen backing plate I4, above which is mounted a screen I and above which is a finer mesh screen I6. The perforations in plate I4 may be A; inch holes on inch centers. The screen I5 may be a 14 mesh wire cloth and the screen I6 may be 45 to 100 mesh. The fineness of the perforations and thescreen mesh may vary according to operating conditions, and the proportions stated merely recite an arrangement which has proven effective for the purposes of the present invention.

The upper edges of the transverse members 8 are very slightly convexed to give sag-proof support to the perforated plate and screens.

A yoke l I connects the two sides 9 and I0 and is rigidly attached as by bolts or rivets I8 to the respective sides. A shaft 20 connects the yoke to a source of differential vibratory movement, such as an electric vibrator 2 I.

It will be noted in Figures 2, 4 and 5 that the frame I is suspended at an acute angle above the horizontal, and in these examples the angle is approximately seven degrees.

Adjacent the lower end of the frame is a water- .tight end assembly 22, having sides 23 that are attached to the sides 9 and ID of the main screen frame assembly. The end 22 is provided with an overflow opening 24 controlled by a weir gate 25 having a discharge launder 2B.

The angle A between the axis of the shaft 20 and the plane of the filter screens, in the examples illustrated, preferably is approximately 45, which in practice has proven effective to produce excellent results, and it will be noted that the planes of the transverse reinforcing members 8 are substantially parallel to the axis of the shaft 20. It will be seen that the entire assembly is built to secure maximum rigidity with minimum weight. It is desirable to stretch the filtering screens and their supporting plate tightly ac oss the frame, as has been explained in detail in our co-pending application, Serial No. 10,670, Patent No. 2,089,548 of August 10, 1937.

All parts are preferably attached together in'a very rigid and secure manner to prevent the possibility of any relative movement or slippage which might dissipate the energy of the vibratory impulses or cause counter-vibrations or vibrations out of harmony with the source. To further insure this'desired result, all structural members are preferably made of material having the same physical carbon steel.

In performing theprocess, a pulp, usually consisting of fine particles of coal of various sizes, suspended in a carrier liquid and which may be the froth concentrate of a flotation operation, or

any other mixture of solids and liquid, is fed into the filter adjacent its lower end, as indicated by the arrow F. This pulp immediately forms a pool, as shown at 28, the depth of which may be selectively governed by the weir gate 25. Differential vibrations are set up in the entire filter assembly, which have the immediate effect of precipitating the particles of solids onto the filter bed to form a cake. Due to the rapid precipitation of the solids from the pulp, there is little or notendency toward hydraulic stratification as to sizes. The cake is therefore composed of all sizes of particles as they happen to be present in the pulp. This feature has been illustrated in Figure 3, in which it will be noted that the larger particle sizes are distributed at all elevations through the solids body.

As the cake 29 forms, the various components of the differential vibrations will cause it to advance upwardly along the filter bed in the direction of arrow B.

The cake itself, being composed of unstratified particles of various sizes, promptly becomes a filtering medium so that suspended particles of infinite fineness may be readily filtered from the pulp even though they are much finer than the mesh of the finest screen in the filter bed. ,As the cake advances upwardly along the screens in a progressive movement, the individual particles are constantly agitated by the vibrations and do not become compact enough to be impervious to water. Water will at all times pass through the cake.

Due to the excellent rigidity of the screen assembly as a whole, the tension in the screens and the free suspension of the filter, the filter cake is precipitated in a layer of even thickness throughout, which in turn reacts most favorably upon the continuation of the filtering process by providing a filtering medium of substantially uniform properties throughout its entire area. As the cake moves progressively out of the pool,

sufiicient time elapses before it reaches the endv of the screen to effect a satisfactory degree of dewatering. When the cake reaches the upper end of the screen it discharges onto a conveyor 3| and is removed thereby. At this stage the compacting has progressed to such a degree that the cake usually retains its shape even after discharge.

In Figure 4, numeral flotation cells into which a pulp of finely divided coal particles and water may be fed, as indicated at arrow D. v

While the filtering treatment of the present invention may be'employed with coal concentrates of flotation, however produced, it has been found in practice that the flotation process described and claimed in Frantz Patent No.

properties, such as low 32 represents a. series of 2,028,742 is very effective for producing a coal concentrate particularly amenable to the dewatering operations of the present invention.

The froth concentrate from this flotation treatment may be delivered to. a pump 33,- the output of which discharges intothe vibrating filter, as indicated at F. The overflow from the filter pool may be delivered into another pump 34 together with the clear filtered liquid that passes through the filter bed to be returned to the flotation stage of the treatment. It is clear that the improved method of dewatering a pulp containing finely divided particles of coal, comprise briefly, the precipitation of the solids onto a filter bed in an unstratified layer, by means of differential vibrations, using this cake as an additional filtering bed and moving the cake upwardly over a further water-extracting medium toward a point of delivery, the porosity of the cake being uniformly maintained by differential vibratory impulses.

The process of the present invention has been described herein with particular reference to the treatment of the coal concentrate of flotation, but it will be understood that any type of loose material in wet condition, and particularly materials having properties corresponding to a coal pulp, may be treated effectively by the present methods.

It will be understood that the production of the pool requires a mixture of solids and liquids,

and so far as the filtering action is concerned,

it is unimportant whether these materials are mixed before filtering or as a part of the filtering operation. Thus solid 'particles containing soluble and insoluble constituents may be treated eficaciously by the present process in which the soluble pulp constituents would be separated from the insoluble and the remaining solid matter dried in a single operation.

Likewise, while the direction of the vibratory impulses with relation to the inclined bottom is an important factor in obtaining best results, it will be apparent that variations through a wide range may be availed of without rendering the treatment inoperative. The particular relation of the component parts of the filter described herein has been found to give highly satisfactory results, but it will be understood that changes in the arrangements of parts, in the proportions of materials, and in the various steps and treatments may be availed of within the spirit and scope of the invention as defined inthe hereunto appended claims.

What we claim and desire to secure by Letters Patent is:

1. The method of separating particles of coal and the like from a liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, 'producing an ungraded settling of particles in .the pool by the discharge of the liquid content through the filtering medium by subjecting the pool todifierential vibratory impulses directed in opposition to the inertia of such pool as approximately 45 to the inclined bottom, compacting the settled" solids on the filtering medium in ungraded condition by a continuance of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body'during its movement along the inclination of the filtering medium upwardly out of the pool induced by repetitions of the vibratory impulses.

2. The method of separating particles of coal and the like from a liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, applying differential vibratory impulses directed in opposition to the inertia of such pool at approximately 45 to the inclined bottom, producing an ungraded settling of particles in the pool by the discharge of the liquid content through the filtering medium under the action oi said differential vibratory impulses, compacting the settled solids on the filtering medium in ungraded condition by a continuance of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body during its movement along the inclination of the filtering mediumupwardly out of the pool induced by repetitions of the vibratory impulses.

3. The method of separating particles of coal and the like from a liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, applying difierential vibratory impulses directed in opposition to the inertia of such pool at approximately 45 to the inclined bottom, producing an ungraded settling of particles in the pool by the discharge of the liquid content through the filtering medium under the action of said differential vibratory impulses, compacting the settled solids on the filtering medium in ungraded condition by a continuance of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body during its movement along the inclination of the filtering medium upwardly out of the pool induced by repetitions of the vibratory impulses uniformly applied throughout its mass.

4. The method of separating particles of coal and the like from the liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, producing an ungraded settling of particles in the pool by the .discharge of the liquid content through the filtering medium by applying to the pool differential vibratory impulses directed in opposition to the inertia of such pool at approximately 45 to the inclined bottom, compacting the settled solids on the filtering medium in ungraded and water-permeable condition by a continuation of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body during its movement alon the inclination upwardly out of the pool induced by repetitions of the vibratory impulses.

5. The method of separating particles of coal and the like from a liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, producing an ungraded settling of particles in the pool by the discharge of the liquid contentat a high velocity through the filtering medium by applying to the pool difierential vibratory impulses directed in opposition to the inertia of such pool at approximately 45 to the inclined bottom, compacting the settled solids on the filtering medium in ungraded condition by a continuation of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body during its movement along the inclination upwardly out of the pool induced by repetitions of the vibratory impulses.

6. The method of separating particles of coal and the like from a liquid with which they are mixed, which comprises the introduction of such a mixture into a suspended pool confined at its sides and supported on its bottom by an inclined filtering medium, producing an ungraded settling of particles in the pool by the discharge of the liquid content through the filtering medium under the action of differential vibratory impulses directed in opposition to the inertia of such pool at approximately 45 to the inclined bottom, said impulses being applied externa ly of the pool in a linear movement in a substantially up and down direction, compacting the settled solids on the filtering medium in ungraded condition by a continuance of such vibratory impulses, and entrapping solids, inclusive of fines, in the compacted body during its movement along the inclination upwardly out of the pool induced by repetitions of the vibratory impulses.

GEORGE H. RUPP. PHILIP M. FRANTZ. 

